The invention relates to the heating and cooling of food items on meal trays in inflight, institutional or similar types of mass feeding operations. In all of such operations it is desirable that the food reach the person for whom it is intended in a tasteful condition with the hot items hot and the cold items cold. A minimum of handling of the trays is also desirable to reduce the labor cost of serving and a minimum of weight is desirable to ease handling and reduce cost. The weight aspect is especially important for inflight feeding systems. Numerous patentees have attempted to resolve the problem but none completely successfully. U.S. Pat. Nos. related to this subject matter include: Reynolds 2,616,269; Hilliker 2,919,339; Bauman 3,042,384; Traycoff 3,129,041; Foster et al 3,199,579; Stenz 3,205,033; Stenz et al 3,275,393; Nicolaus et al 3,389,946; Golden 3,408,481; Shevlin 3,608,627, 3,725,645, 3,784,787 and 3,830,148; Stevenson 3,615,713, Williams 3,908,749; Mack et al 3,924,100; Colato et al 4,005,745; Shumrack et al 4,041,277; Wyatt 4,052,589; Schulz et al U.S. Pat. No. Re. 30,623 and Tricault French Pat. No. 1,219,352. Some of these systems provide separate hot and cold compartments for hot and cold items and require the assembly of the hot items to the tray of cold items before serving. This is wasteful of labor and, in the case of hospitals, can make it possible for a patient on a restricted diet to receive the wrong food items. Others of these patents require heavy, bulky hot food containers which include integral heaters. There are also systems where each food tray must have its own heater elements. Reynolds teaches heating liquid or solid food in a covered container in a refrigerated atmosphere but the food is not on a tray. Others, such as Colato et al U.S. Pat. No. 4,005,745 and the Tricault French Pat. No. 1,219,352 also heat in a refrigerated atmosphere with the food items being on trays and with the hot food container being normally positioned in a hole in the tray which supports its side edges during carrying. The hole permits the hot food container to be positioned directly over a heating element which is located so as to lift the hot container from the tray as it is being heated. This type of system assures excellent direct contact between the heater and container but presents a danger that a person could be burned or could spill the tray if he accidently put his fingers under the hot dish. The danger would be minimal in a hospital where the tray server places the meal on the bed table or onto a second tray but would be much more significant in an aircraft where the passengers often assist in the passing of trays to the window seat. Furthermore, the grabbing of the tray by the passenger on its close edge with his fingers under the entree portion of what he assumes is a solid tray would possibly cause his fingers to propel the entree into his lap or his neighbor's while the rear edge of the tray falls for lack of support, thereby dumping the cold items on someone's legs or the floor. The aforementioned spillage problem could be avoided by using a second tray under the apertured one during serving but this would take assembly time on the part of the server and introduce additional weight to the aircraft. The Schulz et al U.S. Pat. No. Re. 30,623, owned by a common assignee, solves the aforementioned problems by providing a system wherein a heater shelf is slid under a container which is restrained by transverse abutments on the tray. However, the disclosed design still has certain deficiencies which would tend to reduce its degree of acceptance by potential airline customers.